The present invention relates to an indicator which reacts with at least one gaseous compound in such a way that the colour of the indicator is changed.
Publication WO 98/21120 discloses a myoglobin indicator reacting to hydrogen sulphide.
Publications U.S. Pat. No. 6,149,952 and U.S. Pat. No. 5,753,285 disclose an indicator colour combined with a hydrophilic polymer.
Publication U.S. Pat. No. 5,407,829 discloses the development of coloured sulphides from salts of heavy metals. The change in the colour is monitored visually or by means of optoelectonic devices.
Publication JP 2001238696 discloses an indicator intended for detecting Salmonella bacteria in eggs. The indicator is formed by adsorbing a silver, copper or mercury ion by a fibre substance. The indicator will react to gaseous compounds emitted from the egg by a change in the colour.